Top Hydraulics' cylinder rebuild service is widely known as the best possible option, even if you are an excellent Do-It-Yourselfer. Note also our rebuild service for hydraulic valve blocks, distributors, and pumps, as well as manufacture new, superior hydraulic hoses.

DIY cylinder rebuild will usually lead to unintended damage - we have seen thousands of ruined cylinders from failed DIY repair attempts!

We have two order methods: Either you send in your cylinders first, or choose to "Order now with Core Exchange".

Model years 1990-1996 have twelve hydraulic cylinders, while 1997-2002 models have eleven hydraulic cylinders that move and lock the roadster soft top. (The left tonneau cover lock was omitted after 1996.) The original seals in the hydraulic cylinders, aka rams or actuators, will eventually fail in every R129, unless it gets wrecked prematurely, even if you never drive the car or have never used the top before. Rebuilding these cylinders is NOT a matter of changing o-rings. Every R129 cylinder has one o-ring, and those rarely ever fail. What fails most frequently, are the other seals, which have special shapes for proper function.

Top Hydraulics replaces and upgrades ALL seals in the cylinders with our superior proprietary material:

1) Rod seals. They are cup-shaped and seal the piston rod from the rest of the cylinder. When they fail, you will see fluid coming out next to the chromed shaft (rod). These are usually the first seals to fail in the cylinders.

2) Piston seals. They seal the input and output sections from each other, as the piston slides through the cylinder. The piston seals have been made of different materials and sizes even in the same p/n cylinders throughout the years. Failing piston seals will cause internal leaks, which result in a pressure drop in your hydraulic system. Early model years have the added problem that the piston seals swell up and make it very hard to move the piston inside the cylinder. Crumbling piston seals can block valves or pinholes inside the hydraulic system, and it can be difficult to diagnose a piston seal failure without testing several cylinders once you find that your top is moving slowly or not at all.

3) Cap seals. These are just o-rings that seal the top cap of the cylinder from the housing. They are usually the last seals to fail, but these o-rings are penny items.

4) Port seals. They seal the hydraulic lines where they are pushed into the cylinders. Port seal failure is becoming more and more common as the R129s age. It also applies to the front distributor p/n 1298000022. Port seals have a special shape that makes them seal under pressure. O-rings wouldn't do the trick. They are secured by precisely machined brass rings (accuracy about 1/100 mm). DIY removal of the brass rings will almost certainly destroy the brass rings. Top Hydraulics installs port seals that are tighter than the originals, just in case the hydraulic line fittings have been scratched. Cylinders and distributors upgraded by Top Hydraulics should easily outlast your car!

Top Hydraulics remanufactures all hydraulic cylinders for the soft tops and vario roofs on Mercedes convertibles and many other models. We make your cylinders “better than new” with seals superior to those used by the OEM!